Chapter 7

• Development of a New Atomic Model

• The Quantum Model of the Atom

• Electron Configuration

• Periodicity

I. Development of a New Atomic ModelA. Light behaves as both a wave and a particleB. The wave attributes of light include:

1) wavelength - (lamda)the distance from wave to wave (nm)

2) frequency - nunumber of waves per second (s-1; Hz)

3) c* c = 3.00 x 108 m/sec

watch theunits!!!

C. Electromagnetic Spectrum

1) this is the range of all wavelengths/frequencies

and what they are called2) the smaller the wavelength, the more energy it has

Worksheet Problems: # 1,2

D. The particle nature of light - photoelectric effect

1) electromagnetic radiation is emitted in specific

‘packages’ of energy, called photons

2) this radiation does not get to be emitted until the

electrons have obtained a predetermined amount

of minimum energy, called a quantum.

* analogy: a quarter-only coin operated vending machine

Electromagnetic Spectrum

3) The energy associated with a specific wavelength or frequency is:

E = hc

E = h

* wavelength must be in METERS…. frequency in Hz* units for Energy are Joules

Worksheet Problem - # 3

h = 6.636 x 10-34 Js

c = 3.00 x 108 m/s

E. Hydrogen atom line emission spectrum1) ground state - the lowest energy state of an e-2) excited state - higher energy state than ground

state3) the electron in hydrogen are able to be promoted to higher energy levels when given a current4) the color of light given off is made up wavelengths of energy from the electron giving off the energy it absorbed5) the energy released = E2 - E1

6) the resulting spectrum is called a LINE EMISSION SPECTRUM7) The Energy released can be calculated once the wavelength of the emitted photon is known:

Emission Spectrum

II. Quantum Numbers

A. Any mathematical expression with X and Y variables can be graphed to show the relationships between them.

B. An expression with X,Y and Z variables will result in a 3-D graph…..

C. A mathematical equation was used to indicate the probable location of each electron in an atom 1) the variables are called QUANTUM NUMBERS 2) each quantum number is restricted to allow only certain values 3) the mathematical results are numerical answers, but can also be shown graphically (3-D)

D. These are the 4 quantum numbers, meaning and allowed values:

symbol stands for... allowed values comments

n energy level n = 1,2,3... no zero; no -

l shape of 3-D region

l = 0,1,2,3… (n-1) these letters are assigned to each value... s,p,d,f

m orientation of shape

m = - l… 0… + lex: if l = 1, then m = -1, 0, +1

s spin of e- s = + 1/2, - 1/2e- spin is either clockwise or counter clockwise

ex: if n = 1, what l,m and s are allowed?

l = 0 (only)m = 0 (only)… or ‘s’ shapes = +1/2 OR - 1/2

C. So, this is the limit of e- each region can have: s = 2e-…. p = 6e-… d = 10e- … f = 14e-D. The first 3 energy levels are limited in having only some of the shapes: n = 1….. l = 0 (s shape)

n = 2….. l = 0 (s shape) l = 1 (p shape)

n = 3….. l = 0 (s shape) l = 1 ( p shape) l = 2 (d shape)

E. The energy levels fill up in numerical order to start (I.e. all the 1st level, all the 2nd level)…..

ex: 1s2 2s2 2p6

Example 1: Write the electron configuration for these elements:

H = 1 1s

energy level

shape

# e-

He = 1s2

Li = 1s2 2s1

C = 1s2 2s2 2p2

B = 1s2 2s2 2p1

G. How can you determine the order to follow?

1s

2s

3s

4s

5s

6s

7s

2p

3p

4p

5p

6p

7p

3d

4d

5d

6d

7d

4f

5f

6f

7f

This chart is used by following the boxes diagonally from r-l.

F… but then the order depends on energy hierarchies (I.e. its easier to fill some of the 4th before finishing the 3rd)

ex: Write the electron configuration for Calcium

Ca = 1s2 2s2 2p6 3s2 3p6 4s2

H. Miscellaneous topics1) noble gas shortcut - write the previous noble

gas (group 18) symbol in square brackets, then continue from there.

ex: Ca = [Ar] 4s2

2) arrow notation - each orientation is represented by a line…. each electron by an arrow…

ex: 1s2 2s2 2p6 = 1s 2s 2p

1s 2s 2p

3) Hunds Rule - orbitals of equal energy [degenerate orbitals] are filled up equally before a 2nd electron is added.ex: 1s2 2s2 2p4

a) More number of electrons with same spin increases stability

b) as electrons are allowed to occupy separate orbitals, repulsion is minimized

4) Pauli exclusion Principle - two electrons cannot have the same set of 4 quantum numbers

5) Exceptions to electron configuration order

a) Cr - [Ar] 4s1 3d5 [note 1/2 filled s and d orbitals] b) Cu - [Ar] 4s1 3d10 [note 1/2 filled s and filled d]

c) Ag - [Kr] 5s1 4d10 [note 1/2 filled s and filled d]

6) Electron configuration of IONS ….

a) BE SURE to remove OUTERMOST electrons

[valence shell electrons]

ex: Zn = 1s2 2s2 2p6 3s2 3p6 4s2 3d10

Zn+2 = 1s2 2s2 2p6 3s2 3p6 4s2 3d8

Zn = 1s2 2s2 2p6 3s2 3p6 3d10 4s2 [numerical order]

Zn+2 = 1s2 2s2 2p6 3s2 3p6 3d10

x WRONG!

II. Electron Configuration and the Periodic Table

A. Specific regions of the periodic table have similar outer shell electron configuration

ex: What is the outer shell electron configuration for Ba?

ex: What is the outer shell electron configuration for lead?

ex: What is the outer shell electron configuration for silver? (think before you answer)